Keen (kēn), a. [Compar.Keener (–ẽr); superl.Keenest.] [OE. kene sharp, bold, AS. cēne bold; akin to D. koen, OHG. kuoni, G. kühn, OSw. kyn, kön, Icel. kænn, for kœnn wise; perh. akin to E. ken, can to be able. √45.] 1. Sharp; having a fine edge or point; as, a keen razor, or a razor with a keen edge.
A bow he bare and arwes bright and kene. Chaucer.
That my keen knife see not the wound it makes. Shak.
2. Acute of mind; sharp; penetrating; having or expressing mental acuteness; as, a man of keen understanding; a keen look; keen features.
To make our wits more keen. Shak.
Before the keen inquiry of her thought. Cowper.
3. Bitter; piercing; acrimonious; cutting; stinging; severe; as, keen satire or sarcasm.
Good father cardinal, cry thou amen
To my keen curses. Shak.
4. Piercing; penetrating; cutting; sharp; — applied to cold, wind, etc.; as, a keen wind; the cold is very keen.
Breasts the keen air, and carols as he goes. Goldsmith.
5. Eager; vehement; fierce; as, a keen appetite. “Of full kene will.” Piers Plowman.
So keen and greedy to confound a man. Shak.
☞ Keen is often used in the composition of words, most of which are of obvious signification; as, keen-edged, keen-eyed, keen-sighted, keen-witted, etc.
Syn. — Prompt; eager; ardent; sharp; acute; cutting; penetrating; biting; severe; sarcastic; satirical; piercing; shrewd.